The present invention relates to a power working machine, such as a power blower of the type that is used in cleaning operations and delivers a high speed air jet from a blower, and in particular to a power working machine that has a device that detects and visually displays to a user the level of the noise produced by the machine when it is in use.
A power working machine of the above-mentioned kind, such as a power blower, is generally composed of an internal combustion engine, such as a small air-cooled two-stroke gasoline engine, that is mounted on the main body of the blower, a blower fan that is driven by the internal combustion engine, and a blower pipe that is attached to the main body. The power blower is designed to eject a high speed air jet that is generated by the rotation of the blower fan toward the ground from the distal end of the blower pipe. The high speed air jet ejected from the blower pipe is utilized for collecting scattered objects, such as fallen leaves and dust, thus performing a cleaning operation.
FIG. 7 shows one example of a conventional power blower. The power blower 10 has a main body 10a and a blower pipe portion 20. An internal combustion engine 11, such as a small air-cooled two-stroke gasoline engine, is mounted on one side of the main body 10a, and a blower fan 30 of a conventional structure (the details of which are not shown) is mounted on the other side (the side opposite to the side on which the internal combustion engine 11 is mounted) of the main body 10a. The blower fan 30 is coupled to the internal combustion engine 11 so as to be rotationally driven by the internal combustion engine 11.
The main body 10a has a cover 12, which is formed by joining two parts, i.e., a right half cover part 13 and a left half cover part 14. The right half cover part 13 is provided with a cylinder cover 13a for covering the cylinder of the internal combustion engine 11, the cylinder cover 13a being formed integrally with a side portion of the right half cover part 13. The right half cover part 13 and the left half cover part 14 are respectively and integrally provided at their upper portions with a half handle portion of a hollow handle 15, the pair of the half handle portions of the right half cover part 13 and the left half cover part 14 being combined face to face to form the hollow handle 15.
The left half cover part 14 is designed to cover the blower fan 30 and is provided at the center portion thereof with an air inlet port (not shown) for admitting external air and conducting it to the blower fan 30 disposed inside the left half cover part 14. An air-ejecting pipe 16 formed of a combined body of the right half cover part 13 and the left half cover part 14 is positioned at the forward portion of the main body 10a.
The aforementioned blower pipe portion 20 is removably attached to the air-ejecting pipe 16 of the main body 10a.
The blower pipe portion 20 is composed, for example, of a muffler section 21 (as described below, the muffler section 21 is constructed to muffle the noise of the air flow through the blower pipe portion 20) and a discharge section 31. The air inducted through the air inlet port of the left half cover part 14 into the left half cover part 14 is pressurized and delivered by the blower fan 30 and then conducted to the air-ejecting pipe 16.
The air flow pressurized and delivered by a blower fan 30 and introduced into the air-ejecting pipe 16 is then passed through the blower pipe portion 20 so as to be ejected from a flat discharge nozzle 32 which is formed at the distal end of the discharge section 31. The air flow thus ejected from the distal end of the discharge section 31 is utilized for gathering fallen leaves, etc., thereby to perform a cleaning operation.
Inasmuch as the conventional working machine such as a power blower of FIG. 7 is provided with the muffler section 21, it is possible to achieve in some extent an effect of reducing noise. However, it is still required to give a consideration to the noise which may affect the ambient environment where ambient noise is usually relatively low, such as a residential community, so that the operation of the power working machine is inhibited at times other than during the working day time, such as in the evening, at night or in the early morning.
In the present case, some degree of consideration regarding the noise output to the ambient environment may be achieved by lowering the rotational speed of engine on the basis of the operator's perception of the noise level of the machine. However, when a power working machine such as a power blower is operated continuously for a long time, the operator's perception of the noise of a power working machine is frequently diminished, thus reducing his or her ability to give a consideration of the noise being imposed on the ambient environment. Under the circumstances, there is a need to have a way of easily and reliably allowing an operator of a power machine to recognize the level of noise so as to make it possible to suitably restrict the noise level to an amount appropriate for the time of use or the environment of use of the machine.